It is estimated that it currently costs about $1 million per kilogram to put a payload on the lunar surface. Further, limited power generating capability and the subsequent heat load produced by onboard electronic circuitry result in operating issues that constrain the capability of a spacecraft of any given size and configuration. Therefore the cost, size, weight and capability of spacecraft components are always issues of concern. Frequently, trade offs must be made between cost, weight and size and capability.
Spacecraft command and control electronics are indispensable and their complexity increases geometrically as demand for system capability grows. Command and control electronics monitor the condition of various conditions and various components of the spacecraft using a plurality of analog and digital sensors/transducers. The command and control electronics are programmed to make a decision based in part on sensor input and cause the spacecraft to do something via a plurality of mechanical actuators that may be analog or digital devices.
In the analog world, a signal may be derived that represents a particular physical parameter. Non-limiting examples of such parameters include temperature, displacement, pressure, flow rate, force and acceleration. This derivation is accomplished with an appropriately configured sensor or transducer, which converts the physical quantity into an electrical voltage or current. Such sensors are typically located remotely from the command and control electronics and require a signal conditioning system to preprocess the voltage or current for use by the command and control electronics.
Specifically, a signal conditioning system is used to prepare input signals for data acquisition and processing. Signal conditioning includes such exemplary processes as anti-aliasing, amplification, attenuation and filtering. After conditioning, the processed signals may be transmitted to a sample-and-hold circuit that keeps a signal sample stable for subsequent conversion to a digital form by an analog-to-digital converter (AD).
Further, actuators are used in a spacecraft to impart an action that controls the spacecraft. Positional thrusters are but one non-limiting example of actuators onboard a spacecraft. Actuators may be analog devices that are controlled by a digital controller or a processor. To provide analog control signals to the plurality of actuators, each control signal must be converted from a digital form to an analog form, must be processed into a form to properly drive a particular actuator, and then be transmitted to the actuator.
Given that signal processing circuitry is indispensable, it is desirable to minimize the size and weight of any such electronics package to reduce launch costs. In addition, it is desirable to minimize the heat generated by the electronics package. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
Although discussed herein in the context of a spacecraft or satellite, the subject matter disclosed herein may be applied to other types of vehicles or other electronic systems. Any reference to spacecraft applications is merely exemplary and is not intended to limit the scope of the following disclosure in any way.